Mass production method of semiconductor integrated circuit device and manufacturing method of electronic device

ABSTRACT

In order to prevent the contamination of wafers made of a transition metal in a semiconductor mass production process, the mass production method of a semiconductor integrated circuit device of the invention comprises the steps of depositing an Ru film on individual wafers passing through a wafer process, removing the Ru film from outer edge portions of a device side and a back side of individual wafers, on which said Ru film has been deposited, by means of an aqueous solution containing orthoperiodic acid and nitric acid, and subjecting said individual wafers, from which said Ru film has been removed, to a lithographic step, an inspection step or a thermal treating step that is in common use relation with a plurality of wafers belonging to lower layer steps (an initial element formation step and a wiring step prior to the formation of a gate insulating film).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/245,503filed Sep. 18, 2002, now U.S. Pat. No. 6,586,161, which is acontinuation of application Ser. No. 09/635,569 filed Aug. 9, 2000.

BACKGROUND OF THE INVENTION

This invention relates to a mass production technique of a semiconductorintegrated circuit device, and more particularly, to a techniqueeffectively applicable to a semiconductor production process, in whichwhen a large number of wafers are continuously processed over aplurality of steps, the process is carried out in a mass production linewherein the lithographic step of wafers on which a film containing atransition metal such as ruthenium (Ru) is deposited and thelithographic step of wafers belonging to other steps are commonly used.

In the industrial fields other than that of the manufacture of asemiconductor, there is known a technique wherein a platinum groupelement is dissolved in a dissolution solution and isolated for thepurpose of collecting the platinum group element from wastes or thelike.

Japanese Laid-open Patent Publication No. Hei 7-157832 (Ito et al.)discloses a technique of recovering noble metals, such as gold, platinumgroup elements and the like, from used electronic parts, noblemetal-containing, wasted catalysts, and a used jewelry by dissolutionthereof in a dissolving solution. For the dissolution of noble metals,there is used a dissolving solution which is obtained by mixing anaqueous solution of an inter-halogen compound (e.g. ClF, BrF, BrCl, ICl,ICl₃, IBr or the like) and an aqueous solution of a halogenated oxoacid(iodic acid, bromic acid, chloric acid or the like) at a ratio in therange of 1:9 to 9:1 The noble metal dissolved in the solution is firstseparated as a halogenated complex, to which a solution of a compound(e.g. sodium hydroxide, sodium borohydride, hydrazine or its salt,sulfurous acid or its salt, a bisulfite or the like) is then added,thereby collecting the metal.

Japanese Laid-open Patent Application No. Hei 7-224333 (Wada et al)discloses a technique of dissolving out, in the form of an aqueoussolution, an alloy formed by nuclear fission and containing noblemetals, such as ruthenium (Ru), rhodium (Rh), palladium (Pd) withoutundergoing such a pretreatment as by liquid metal extraction byimmersing the alloy in a dissolving solution of hydroiodic acid (orhydrobromic acid), to which an iodine simple element is added. It isstated that the dissolving solution has a concentration of hydroiodicacid (or hydrobromic acid) ranging from 5 to 57 wt %, and aconcentration of the added iodine simple element ranging from 0.01 to0.5 moles per liter of the former aqueous solution.

SUMMARY OF THE INVENTION

In order to ensure an accumulated charge quantity of finely dividedmemory cells, a great capacitance DRAM (Dynamic Random Access Memory) of1 Gbit or over has a capacitance insulating film of an informationstorage capacitor constituted of a high dielectric material such as anABO₃-type composite oxide having a specific inductive capacity of 100 orover, i.e. a perovskite composite oxide of BST (Ba, Sr) TiO₃) For use asa capacitance insulating film material of the next generation, studieshave been made on ferrodielectric materials having a perovskite crystalstructure such as of PZT (PbZr_(x)Ti_(1-x)O₃), PLT (PbLa_(x)Ti_(1-x)O₃),PLZT, SBT, PbTiO₃, SrTiO₃ and BaTiO₃.

Where such a high/ferrodielectric material is used for the capacitanceinsulating film of a capacitor, it is necessary that conductive filmsfor upper and lower electrodes sandwiching the capacitance insulatingfilm therebetween should be each made mainly of a metal having highaffinity for the high/ferrodielectric material, e.g. a platinum groupmetal (e.g. Ru (ruthenium), Rh (rhodium), Pd (palladium), Os (osmium),Ir (iridium) or Pt (platinum). Especially, ruthenium (Ru) is consideredto be full of promise for use as an electrode material of a capacitorwherein the capacitance insulating film is constituted of such ahigh/ferrodielectric material because of its excellent etchingcontrollability and film stability.

On the other hand, as a countermeasure for preventing an increase inwiring resistance caused by the scale down of a wiring width and thelowering of reliability in the field of high-speed logic LSI's, therehas now been introduced copper wirings buried according to a so-calledDamascene method. In the method, wiring grooves (and through-holes) areformed in an insulating film deposited on a substrate, and a copper (Cu)film having an electric resistance lower than an Al film is deposited onthe insulating film including the inner surfaces of the wiring grooves(and the through-holes), followed by removal of an unnecessary copperfilm outside of the wiring grooves by a chemical mechanical polishing(CMP) method, the introduction of the buried copper wirings is now understudy not only in the field of logic LSD, but also in the field ofmemories such as DRAM.

However, in order to introduce newcomer transition metals, such as theabove-mentioned platinum group metals, perovskite-typehigh/ferrodielectrics and copper, which have never been in use in knownwafer processes, and materials comprising the transition metals, into asemiconductor production process, it is essential to take a measure forpreventing wafers from contamination with these transition metals.Especially, a transition metal such as copper has a great coefficient ofdiffusion in silicon (Si) and readily arrives at a substrate whenundergoing an annealing step (thermal treatment step), with the greatapprehension that it gives a serious adversely influence on devicecharacteristics even at a very small concentration.

For instance, in the manufacturing process of general-purpose LSI's suchas DRAM, a facility investment is suppressed to a minimum to reduceproduct costs, so that lithographic devices (such as a light exposuredevice and an EB exposure device), various types of inspection devices,and an annealing (thermal treating) device are commonly used in aninitial element-forming step and a wiring step prior to the formation ofa gate insulating film. These common devices are employed in the step offorming capacitors by use of such a newcomer material as set outhereinabove. More particularly, after transfer, from the common devices,of a wafer used for carrying out the capacitor-forming step, a freshwafer used for carrying out the initial element-forming step or used forcarrying out the wiring step is, in turn, transferred into the devices.In case where the buried copper wiring formed according to the Damascenemethod is provided as the wiring formed as an upper layer of thecapacitor, a wafer having a copper film deposited on as an upper layerof the capacitor is transferred to the common devices for annealing(thermal treatment) after or prior to the transfer of another wafer tobe subjected to other steps.

A film containing a platinum group metal, a perovskite-typehigh/ferrodielectric material or a transition metal such as copper,which has been deposited on the device side of a wafer according to asputtering method or a CVD method, is also deposited on the outermarginal portions (edge portions) or the back side of the wafer. In thiscondition, when the wafer, from which the transition metal-containingfilm deposited on the outer edge portions or the back side of the wafer,is transferred to the common devices without removing the film to asatisfactory extent, a wafer stage, a wafer carrier, a conveyor and thelike, which has come into contact with the outer edge portion or theback side of the wafer, are deposited on the surface thereof with thetransition metal-containing film. This results in the contamination,with the transition metal, of a wafer which will be subsequentlytransferred to the common devices for performing lower layers steps(such as the step of forming an initial element and the wiring stepprior to the formation of a gate insulating film).

Accordingly, in the mass production line for carrying out, by use of thecommon devices, the lithographic step for the wafer deposited thereonwith a transition metal-containing film as stated above and thelithographic step for the wafers belonging to other steps including thelower layers steps, it is essential to provide a cleaning step ofremoving the transition metal-containing film deposited on the outeredge portions and the back side of a wafer prior to the transfer of thetransition metal-containing film-deposited wafer.

However, a solution for dissolving, for example, ruthenium among theafore-indicated transition metals has not been found so that aneffective cleaning method therefor has not been established yet. Ashaving set out before, several types of solutions for dissolvingplatinum group metals have been proposed in the industrial fields otherthan that of the manufacture of semiconductor. However, these dissolvingsolutions are so low in dissolving rate of ruthenium that they cannot beused in the mass production line of semiconductor.

Another measure for preventing the contamination of a wafer with atransition metal is to provide an exclusive device for carrying out thelithographic step for the wafer deposited with a transitionmetal-containing film, separately from the common devices. Nevertheless,this is not of practical value from the standpoint of reduction inproduction cost.

An object of the invention is to provide a technique of reliablypreventing the inconvenience of a wafer being contaminated with atransition metal when the wafer is subjected to an initial elementformation step and a wiring step in the semiconductor mass productionline wherein an initial element formation step and a wiring step, and alithographic device, inspection devices, an annealing (thermal treating)device and the like in a transition metal-containing film processingstep are commonly used prior to the formation of a gate insulating film.

This and other objects and features of the invention will becomeapparent from the description of the invention with reference to theaccompanying drawings.

Of the embodiments disclosed in the invention, typical ones are brieflydescribed or summarized below.

The mass production of a semiconductor integrated circuit device of theinvention comprises the steps of:

(a) depositing a Ru film on individual wafers being in passage of awager process

(b) removing the Ru film from outer edge portions on a device side ofthe individual wafers, on which the Ru film has been deposited, and aback side thereof with use of a solution containing an orthoperiodicacid; and

(c) subjecting the individual wafers, from which the Ru film has beenremoved, to a lithographic step, an inspection step or a thermaltreating step which is in common use with plural types of wafersbelonging to lower layers steps.

The summary of the invention other than the above-stated one is brieflyitemized as numbered below.

1. A mass production method of a semiconductor integrated circuit devicecomprising the steps of:

(a) depositing a platinum group metal film on a device side of a firstwafer among a plurality of wafers passing through a wafer process;

(b) removing the platinum group metal film from outer edge portions ofthe device side or a back side of the first wafer, on which the platinumgroup metal film has been deposited;

(c) patterning, after the step (b), the platinum group metal film on thedevice side of the first wafer through an etching-resistant mask patternformed in a lithographic step;

(d) depositing a film to be processed different in type from theplatinum group metal film on a device side of a second wafer among theplurality of wafers passing through the wafer process; and

(e) patterning the film to be processed, which has been deposited on thedevice side of the second wafer, by the lithographic step.

2. A mass production method of a semiconductor integrated circuit deviceas recited in 1 above, characterized in that the platinum group metalfilm is made of a ruthenium film.

3. A mass production method of a semiconductor integrated circuit deviceas recited in 1 or 2 above, characterized in that the step of patterningthe film to be processed is a lower layer step in comparison with thestep of patterning the platinum group metal film.

4. A mass production method of a semiconductor integrated circuit deviceas recited in any one of 1 to 3 above, characterized in that theplatinum group metal film is removed by use of a solution containing anorthoperiodic acid.

5. A mass production method of a semiconductor integrated circuit deviceas recited in any one of 1 to 4 above, characterized in that theplatinum group metal film is removed by use of a solution containing anorthoperiodic acid and a second acid.

6. A mass production method of a semiconductor integrated circuit deviceas recited in 5 above, characterized in that the second acid is made ofnitric acid.

7. A mass production method of a semiconductor integrated circuit deviceas recited in 6 above, characterized in that the solution has aconcentration of orthoperiodic acid of 20 wt % to 40 wt %, and aconcentration of nitric acid of 20 to 40 wt %.

8. A mass production method of a semiconductor integrated circuit deviceas recited in 6 above, characterized in that the solution has aconcentration of orthoperiodic acid of 25 wt % to 35 wt %, and aconcentration of nitric acid of 25 to 35 wt %.

9. A mass production method of a semiconductor integrated circuit deviceas recited in 5 above, characterized in that the second acid is made ofacetic acid.

10. A mass production method of a semiconductor integrated circuitdevice as recited in any one of 1 to 9 above, characterized in that theplatinum group metal film is removed, at least, from substantially anentire surface of the back side of the individual wafers and the outeredge portions of the device side.

11. A mass production method of a semiconductor integrated circuitdevice comprising the steps of:

(a) depositing a transition metal-containing film on a device side of afirst wafer among a plurality of wafers passing through a wafer process;

(b) removing the transition metal-containing film from outer edgeportions of the device side or a back side of the first wafer, on whichthe transition metal-containing film has been deposited;

(c) patterning, after the step (b), the transition metal-containing filmon the device side of the first wafer through an etching-resistant maskpattern formed in a lithographic step;

(d) depositing a film to be processed different in type from thetransition metal-containing film on a device side of a second waferamong the plurality of wafers passing through the wafer process; and

(e) patterning the film to be processed, which has been deposited on thedevice side of the second wafer, by the lithographic step.

12. A mass production method of a semiconductor integrated circuitdevice as recited in 11 above, characterized in that the transitionmetal-containing film is made of a perovskite-type high dielectricmaterial or ferrodielectric material.

13. A mass production method of a semiconductor integrated circuitdevice as recited in 12 above, characterized in that the perovskite-typehigh dielectric material or ferrodielectric material is made of BST.

14. A mass production method of a semiconductor integrated circuitdevice as recited in 11 above, characterized in that the perovskite-typehigh dielectric material or ferrodielectric material is PZT, PLT, PLZT,SBT, PbTiO₃, SiTiO₃ or BaTiO₃.

15. A mass production method of a semiconductor integrated circuitdevice as recited in 11 above, characterized in that the transitionmetal is made of copper.

16. A mass production method of a semiconductor integrated circuitdevice comprising the steps of:

(a) depositing a Ru film on a device side of a first wafer among aplurality of wafers passing through a wafer process;

(b) removing the Ru film from outer edge portions of the device side ora back side of the first wafer, on which the Ru film has been deposited;

(c) patterning, after the step (b), the Ru film on the device side ofthe first wafer through an etching-resistant mask pattern formed in alithographic step, thereby forming a capacitor electrode;

(d) depositing a film to be processed different in type from the Ru filmon a device side of a second wafer among the plurality of wafers passingthrough the wafer process; and

(e) patterning the film to be processed, which has been deposited on thedevice side of the second wafer, by the lithographic step.

17. A mass production method of a semiconductor integrated circuitdevice as recited in 16 above, characterized in that the step ofpattering the film to be processed is a lower layer step downstream ofor in comparison with the step of patterning the Ru film.

18. A mass production method of a semiconductor integrated circuitdevice as recited in 16 or 17 above, characterized in that the Ru filmis removed by use of a solution containing orthoperiodic acid.

19. A mass production method of a semiconductor integrated circuitdevice as recited in 16 or 17 above, characterized in that the Ru filmis removed by use of a solution containing an orthoperiodic acid and asecond acid.

20. A mass production method of a semiconductor integrated circuitdevice as recited in 19 above, characterized in that the second acid ismade of nitric acid.

21. A mass production method of a semiconductor integrated circuitdevice as recited in 20 above, characterized in that the solution has aconcentration of orthoperiodic acid of 20 wt % to 40 wt %, and aconcentration of nitric acid of 20 to 40 wt %.

22. A mass production method of a semiconductor integrated circuitdevice as recited in 20 above, characterized in that the solution has aconcentration of orthoperiodic acid of 25 wt % to 35 wt %, and aconcentration of nitric acid of 2.5 to 35 wt %.

23. A mass production method of a semiconductor integrated circuitdevice comprising the steps of:

(a) depositing a Ru film on a device side of a first wafer among aplurality of wafers passing through a wafer process;

(b) removing the Ru film from outer edge portions of the device side ora back side of the first wafer, on which the Ru film has been deposited,by use of a solution containing orthoperiodic acid;

(c) patterning, after the step (b), the Ru film on the device side ofthe first wafer through an etching-resistant mask pattern formed in alithographic step, thereby forming a capacitor electrode of DRAM;

(d) depositing a film to be processed different in type from the Ru filmon a device side of a second wafer among the plurality of wafers passingthrough the wafer process; and

(e) patterning the film to be processed, which has been deposited on thedevice side of the second wafer, by the lithographic step.

24. A mass production method of a semiconductor integrated circuitdevice as recited in 23 above, characterized in that the step ofpattering the film to be processed is a lower layer step downstream ofor in comparison with the step of patterning the Ru film.

25. A mass production method of a semiconductor integrated circuitdevice as recited in 24 above, characterized in that the step ofpatterning the film to be processed is a step of forming a gateelectrode or a step of forming a bit line.

26. A mass production method of a semiconductor integrated circuitdevice as recited in any one of 23 to 25 above, characterized in thatthe Ru film is removed by use of a solution containing orthoperiodicacid and nitric acid.

27. A mass production method of a semiconductor integrated circuitdevice as recited in 26 above, characterized in that the solution has aconcentration of orthoperiodic acid of 20 wt % to 40 wt %, and aconcentration of nitric acid of 20 to 40 wt %.

28. A mass production method of a semiconductor integrated circuitdevice as recited in 27 above, characterized in that the solution has aconcentration of orthoperiodic acid of 25 wt % to 35 wt %, and aconcentration of nitric acid of 25 to 35 wt %.

29. A mass production method of a semiconductor integrated circuitdevice comprising the steps of:

(a) depositing a film containing a transition metal made of aperovskite-type high dielectric material or ferrodielectric material ona device side of a first wafer among a plurality of wafers passingthrough a wafer process;

(b) removing the transition metal-containing film from outer edgeportions of the device side or a back side of the first wafer, on whichthe transition metal-containing film has been deposited;

(c) patterning, after the step (b), the transition metal-containing filmon the device side of the first wafer through an etching-resistant maskpattern formed in a lithographic step, thereby forming a capacitanceinsulating film of a capacitor of DRAM;

(d) depositing a film to be processed different in type from thetransition metal-containing film on a device side of a second waferamong the plurality of wafers passing through the wafer process; and

(e) patterning the film to be processed, which has been deposited on thedevice side of the second wafer, by the lithographic step.

30. A mass production method of a semiconductor integrated circuitdevice as recited in 29 above, characterized in that the perovskite-typehigh dielectric material or ferrodielectric material is made of BST.

The general meanings of the terms used in the present invention areillustrated below.

1. The term “CMIS integrated circuit” is intended to mean an integratedcircuit made of a complementary insulation gate-type FET including,aside from general CMOS integrated circuits, devices having a gateinsulating film made, for example, of a dielectric material other thanan oxide film such as silicon nitride or tantalum oxide.

2. The term “device side” means a main surface of a wafer, on which anintegrated circuit pattern corresponding to a plurality of chip regionsis formed by photolithography. That is, “device side” is an oppositeside of “back side”.

3. The term “buried wiring” means one wherein a groove is formed in aninsulating film as in single Damascene or dual Damascene, and aconductive film such as copper is buried in the groove, followed byremoval of an unnecessary conductive film through patterning by awiring-forming technique.

4. The term “semiconductor integrated circuit water” or “semiconductorwafer” is intended to mean a silicon single crystal substrate (usually,substantially in a circular form), a sapphire substrate, a glasssubstrate, other insulating, anti-insulating and semiconductivesubstrates, and composite substrates thereof. The term “semiconductorintegrated circuit device” (or “electronic device”, “electronic circuitdevice” and the like) means not only a device formed on a single crystalsilicon substrate, but also those devices formed on various types ofabove-mentioned substrates, or other types of substrates including anSOI (silicon on insulator) substrate, a TFT (thin film transistor)liquid crystal-manufacturing substrate, an STN (super twisted nematic)liquid crystal-manufacturing substrate and the like unless otherwiseindicated.

5. The term “chip-forming portion” means a portion including a pluralityof chip regions on the device side of a wafer, indicating an innerregion except “an outer edge portion” where it is not intended to make aperipheral chip”.

6. The term “high dielectric material” means a high dielectric materialhaving a specific inductive capacity of 20 or over, such as Ta₂O₅, and ahigh dielectric material having a specific inductive capacity exceeding100, such as BST ((Ba, Sr) TiO₃).

7. The term “ferrodielectric material” means PZT, PLT, PLZT, SBT,PbTiO₃, SrTiO₃ and BaTiO₃, which, respectively, have a perovskitestructure in a ferrodielectric phase at normal temperatures.

8. The term “transition metal” generally means elements of group 3, towhich yttrium, lanthanum and the like belong, to group 11, to whichcopper and the like belongs, of the periodic table. The term “transitionmetal-containing film” means a film which comprises a materialcontaining a transition metal, or a transition metal as a major or minorproportion of an constituent element (e.g. Ru, RuO₂, Ta₂O₅ and thelike). The term “transition metal-containing film deposition treatment”means a treatment wherein the above-mentioned transitionmetal-containing film is attached to or deposited purposely orunintentionally. Accordingly, the treatment includes, aside from thestep of depositing an insulating film or a metal film, an etching step.In the practice of the invention, the term “harmful transition metal”means one which is not adequately evidenced with respect to the natureas a contaminant among transition metals employed in a semiconductorprocess and is selected, for example, from platinum and copper groupelements. Moreover, the term “made of copper” used herein is not limitedto pure copper alone, but includes copper containing other constituentelement, additive, impurity and the like in amounts not impeding thefunction thereof unless otherwise indicated.

9. The term “platinum group element” generally means ruthenium, rhodium,palladium, osmium, iridium and platinum among the elements generallybelonging to the groups 8 to 10 of the periodic table.

10. The term “lower layers steps” used in a wafer process means a groupof a series of steps including the step of formation of a film to beprocessed, the step of formation of a resist, the steps of exposure,development and patterning of the film, and the like precedent to anintended step when attention is paid to one wafer. For instance, lowerwiring steps are a lower layer process or step in comparison with upperwiring steps. The reverse is called “upper layer steps”. It will benoted that these definitions do not always mean a physical upstream ordownstream relationship.

11. The term “lithographic step” means that with the case of lightexposure, for example, the step covers from the step of coating aphotoresist onto a wafer after the step of formation of a given film tothe step of exposing the photoresist to light and developing the exposedphotoresist (including the baking step, if necessary) The common userelation in the lithographic step means the relation where wafersbelonging to different steps pass through a lithographic step made ofthe same arrangement. In this case, the same arrangement does notinclude all devices in common use. One of devices, e.g. an exposuredevice (e.g. a light exposure device, an EB exposure device or thelike), may be in common use.

12. The term “mass production” in a wafer line generally means athroughput of approximately 1000 wafers/day. In the practice of theinvention, taking the tendency toward a large-sized wafer into account,a throughput of approximately 100 wafers/day is included for the massproduction. In this case, it is as a matter of course that the same typeof wafer is used for the purpose.

13. The-term “chemical mechanical polishing (CMP)” generally means onewherein while a surface to be polished is in contact with a polishingpad made of a relatively soft cloth-like sheet material under which aslurry is supplied, they are relatively moved along the surface. Beside,CML (chemical mechanical lapping), in which a surface to be polished ismoved relative to the surface of a hard grind stone, may be included inthe practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to one embodiment of the invention;

FIG. 2 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 3 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 4 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 5 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 6 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 7 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 8 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 9 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 10 is a view illustrating a concept of common use of a lithographicstep in a mass production process of a semiconductor integrated circuitdevice;

FIG. 11 is a sectional view showing a peripheral portion of a wafer onwhich an Ru film is deposited;

FIG. 12 is a schematic sectional view showing an example of a cleaningdevice used in the one embodiment of the invention;

FIG. 13 is a plan view showing the stage of the cleaning device shown inFIG. 12;

FIG. 14 is a schematic sectional view showing a method of holding awafer in the cleaning device-shown in FIG. 12;

FIG. 15 is a table showing the etching rate of Ru depending on differenttypes of cleaning solutions used in a semiconductor production process;

FIG. 16 is a table showing the etching rate of Ru depending on differenttypes of oxidizing agents;

FIG. 17 is a table and a graph showing the relation between theconcentration of an orthoperiodic acid aqueous solution and the etchingrate of Ru;

FIG. 18 is a table and a graph showing the relation between theconcentration of nitric acid and the etching rate when Ru is etched byuse of an orthoperiodic acid aqueous solution to which nitric acid isadded;

FIGS. 19(a) to 19(d) are, respectively, a table showing the relationbetween the mixing ratio of nitric acid and the etching rate when Ru isetched by use of an orthoperiodic acid aqueous solution, to which anitric acid aqueous solution is added;

FIG. 20 is a graph showing, as a contour, the etching rate of Ru with asolution obtained by adding a nitric acid aqueous solution to anorthoperiodic acid aqueous solution;

FIG. 21 is a table showing the variation in etching rate of Ru whendifferent types of commercially available acids are, respectively, addedto an orthoperiodic acid aqueous solution;

FIG. 22 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 23 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 24 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 25 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 26 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 27 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIG. 28 is a sectional view of an essential part of a semiconductorsubstrate showing a mass production method of a semiconductor integratedcircuit device according to the one embodiment of the invention;

FIGS. 29(a) and 29(b) are, respectively, a view illustrating thedifference in behavior between the oxidizing agent capable of releasingoxygen atoms and the oxidizing agent incapable of releasing oxygenatoms;

FIG. 30 is a view illustrating processing steps of a ruthenium thin filmaccording to a second example; and

FIG. 31 is a view illustrating a cleaning step of ruthenium fineparticles according to a third example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the invention are described in detail with referenceto the accompanying drawings. It should be noted that throughout thedrawings illustrating the embodiments, like reference numerals,respectively, indicate like members having the same functions, and arenot repeatedly illustrated. In the following embodiments, the same orsimilar parts or portions are not basically described repeatedly exceptthe case of necessity.

In the following embodiments, if need be for convenience's sake, aplurality of sections or division into embodiments is illustrated. Withthe exception of the case indicated specifically, these are not mutuallyunrelated, and one may be in relation with variations and detailed andsupplementary description relative to part or all of others. Moreover,in the following embodiments, where reference is made to the number ofelements (including the number, value, amount, range and the like), itshould not be construed as limiting to a specified number unlessotherwise indicated or except the case where such a number isprincipally, apparently limited to the specified number. The number overor below the specified number may be within the scope of the invention.In addition, in the following embodiments, the constituting elements(including elemental steps) are not necessarily essential unlessotherwise indicated or except the case where such elements areprincipally, apparently essential.

Likewise, in the following embodiments, where reference is made to theshape and positional relation of a constituting element, thosesubstantially close or similar to the shape and the like are within thescope of the invention unless otherwise indicated or except the casewhere such is not a case principally and apparently. This is true of thenumerical values and their ranges.

EXAMPLE 1

The production process of DRAM according to an embodiment of theinvention is described step by step with reference to FIGS. 1 to 28.

As shown in FIG. 1, after formation of an element isolation groove 2 ina main surface of a semiconductor substrate (wafer) 1 made, for example,of p-type single crystal silicon having a specific resistance ofapproximately 10 Ωcm, a p-type well 3 is formed in the substrate 1. Theelement isolation groove 2 is formed by forming a groove by dry etchingof the substrate 1 at an element isolation region thereof, depositing asilicon oxide film 4 over the substrate 1 including the inside of thegroove according to a CVD method and polishing the silicon oxide film 4by a chemical mechanical polishing (CMP) method to leave it in thegroove. The p-type well 3 is formed by ion implanting an n-typeimpurity, e.g. P (phosphorus) into the substrate 1 and annealing(thermally treating) the substrate 1 to permit the n-type impurity to bediffused.

Next, the p-type well 3 is cleaned on the surface thereof with ahydrofluoric acid-based (HF) cleaning solution, after which thesubstrate 1 is wet oxidized to form a clean gate oxide film 5 on thesurface of the p-type well 3.

As shown in FIG. 2, a gate electrode 6 (word line WL) is formed on thetop of the gate oxide film 5, followed by formation of an n-typesemiconductive region 7 of a low impurity concentration on the p-typewell 3 at the opposite side of the gate electrode 6.

The gate electrode 6 (word line WL) is formed by depositing, on thesubstrate 1, a polysilicon film doped with an n-type impurity such as,for example, P according to a CVD method, depositing, on the topthereof, a WN (tungsten nitride) film and a W (tungsten) film by asputtering method, further depositing a silicon nitride film 8 thereoverby the CVD method, and dry etching these films by the mask of aphotoresist film. The n-type semiconductive region 7 is formed by ionimplantation of an n-type impurity such as, for example, arsenic (As).

Thereafter, as shown in FIG. 3, a silicon nitride film 9 and a siliconoxide film 10 are successively deposited over the substrate 1 by a CVDmethod, followed by planarization of the silicon oxide 10 on the surfacethereof by a chemical mechanical polishing method.

Next, as shown in FIG. 4, using a photoresist film (not shown) as amask, the silicon oxide film 10 and the silicon nitride film 9 above thesemiconductive region 7 are dry etched to form contact holes 11, 12.Subsequently, as shown in FIG. 5, a plug 13 made of a polysilicon isformed inside the contact holes 11, 12. The plug 13 is formed bydepositing, for example, inside the contact holes 11, 12 and over thesilicon oxide film 10, a polysilicon film doped with an n-type impuritysuch as P by a CVD method, after which the polysilicon film is removedfrom the top of the silicon oxide film 10 by a chemical mechanicalpolishing (or etching-back) method, and left inside the contact holes11, 12.

Thereafter, the substrate is annealed (thermally treated) so that then-type impurity in the polysilicon film serving as the plug 13 isdiffused into the substrate 1 (n-type semiconductive region 7), therebyforming n-type semiconductive regions (source, drain) of a high impurityconcentration. According to the steps set out hereinabove, MISFEQs ofthe n-channel type for memory cell selection, which constitute part of amemory cell of DRAM are completed.

Next, as shown in FIG. 6, a silicon oxide film 15 is deposited over thesilicon oxide film 10 according to a CVD method, and the silicon oxidefilm 15 is subsequently dry etched to form a through-hole 16 above thecontact hole 11, followed by forming a plug 17 inside the through-holeand further forming a bit line BL over the plug 17.

The plug 17 is formed by depositing a TiN (tungsten nitride film and a Wfilm, for example, inside the through-hole 16 and above the siliconoxide film 15 by a CVD method or sputtering method, followed by removingthe TiN film and W film on the silicon oxide film 15 by a chemicalmechanical polishing method to leave them inside the through-hole 16.The bit line BL is formed, for example, by depositing a W film on thesilicon oxide film 15 by a sputtering method and dry etching the W filmthrough the mask of a photoresist film. The bit line BL is electricallyconnected to either (the n-type semiconductive region 14) of the sourceand drain of MISFETQs for memory selection through the plug 17 withinthe through-hole 16 and the plug 13 within the contact hole 11.

Next, as shown in FIG. 7, a silicon oxide film 18 is deposited on thesilicon oxide film 15 by a CVD method, and a TiN film 19 is furtherformed on the silicon oxide film 18 by a sputtering method, followed bydry etching of the TiN film 19 and the silicon oxide film 18 to form athrough-hole 20 over the contact hole 12, followed by formation of aplug inside the through-hole 20. The plug 21 is formed, for example, bydepositing a polysilicon film doped with an n-type impurity, such as P,inside the through-hole 20 and on the TiN film 19 by a CVD method, andthe polysilicon film on the TiN film 19 is removed by an etching-backmethod to leave it inside the through-hole 20. At this time, thepolysilicon film constituting the plug 21 is over-etched so that thesurface of the plug 21 is recessed relative to the surface of the TiNfilm.

Next, as shown in FIG. 8, a barrier metal 22 is formed on the plug 21.The barrier metal 22 is formed, for example, by depositing a WN filminside the through-hole 20 and on the TiN film 10 by a sputteringmethod, and the WN film on the TiN film is removed by a chemicalmechanical polishing (or etching-back) method to leave the W film insidethe through-hole 20.

The barrier metal on the plug 21 is formed for the purposes ofpreventing the reaction between a lower electrode material (Ru) of aninformation storage capacitor element deposited on the TiN film 19 in asubsequent step and the plug 21 (polysilicon film) and preventingoxidation of the plug 21 (polysilicon film) with oxygen present in acapacitance insulating film material (BST). The barrier metal 22 may beconstituted, aside from WN, of TiN, TaN (tantalum nitride), TaSiN, WSiN,TiSiN or the like.

As shown in FIG. 9, a Ru film serving as a lower electrode of aninformation storage capacitor element is deposited on the TiN film by asputtering method.

In the production process of general-purpose LSI such as DRAM,lithographic devices (a light exposure device and an EB exposuredevice), various inspection devices, an annealing (thermal treating)device and the like are commonly used for the initial element formationstep and wiring step prior to the formation of a gate insulating film inorder to suppress a facility investment to a minimum and reduce theproduction cost, as is particularly shown in FIG. 10. In the formationof an information storage capacitor element wherein transition metals ormaterial containing the metals, such as the Ru film 23 and a BST filmdescribed hereinafter, which have never been used in prior art waferprocesses, there common use devices are employed. Accordingly, the wafer(substrate) 1, on which the Ru film 23 or the BST film has beendeposited, is transferred from a device, after which the wafer 1 istransferred to the common use devices for carrying out an initialelement formation step or wiring step. The term “wiring step” usedherein means the step of forming the gate electrode 6 and the bit lineBL shown in FIGS. 2 to 8 and the step of forming wirings on aninformation storage capacitor element described hereinafter.

FIG. 11 is a sectional view showing a peripheral portion of the wafer 1on which the Ru film is deposited. As shown, the Ru film 23 is depositedon the device side (main surface) of the wafer (substrate) 1 by asputtering method, whereupon the Ru film 23 is deposited not only on achip formation portion on the device side and an outer edge portion, butalso on a side surface (edge portion). Part of the film is deposited onthe back side of the wafer 1. In this condition, when the wafer 1 istransferred to the common use devices without satisfactory removal ofthe Ru film from the side surface and the back side thereof, a waferstage, wafer carrier, conveyor and the like, which come into contactwith the side surface and the back side, are attached with the Ru film23 on the surfaces thereof. This results in the contamination, with Ru,of the wafers 1 of the lower layers steps (including the initial elementformation step and wiring step prior to the gate insulating filmformation step, which are subsequently fed to the common use devices).

In this embodiment, prior to the step of forming a lower electrode aftertransfer of the wafer, on which the Ru film 23 is deposited, to thecommon use devices, the unnecessary Ru film 23 deposited on the sidesurface and the backside of the wafer 1 is removed in the following way.

FIG. 12 is a schematic sectional view showing an example of a cleaningdevice used to remove the Ru film 23 deposited on the side surface andthe back side of the wafer 1, and FIG. 13 is a plan view showing thestage of the cleaning device.

A cleaning device 100 includes a treating chamber 101 having a stage102, on which the wafer 1 is mounted, at a central portion thereof. Thestage 102 has, on the upper surface thereof, four pins 103 which are incontact with the side surfaces of the wafer 1 and are located at equalintervals. These pins 103 are arranged to be rotated thereabout within ahorizontal plane. The wafer 1 is horizontally held in such a state thatits back side is turned upwardly by urging the pins 103 against thewafer. The wafer 1 supported with the pins 103 is in a non-contact statewith the stage 102 except for the four side surfaces in contact with theindividual pins 103.

There are provided, below the treating chamber 101, a drive unit 104capable of rotating the stage 102 within the horizontal plane and a gasfeed unit 105 filled with an inert gas such as nitrogen. The nitrogengas in the gas feed unit 105 is supplied to the upper surface of thestage 102 through a pipe 106 below the stage 102.

As shown in FIG. 14, the four pins 103 arranged above the stage 102 canbe, respectively, moved horizontally in a direction kept away from thewafer. When the wafer 1 is held with the four pins 104, these pins 103have been preliminarily moved at positions remote from the wafer 1,under which the nitrogen gas is fed against the lower surface of thewafer 1 to permit the wafer to be floated. In this state, the pins 103are urged against the side surfaces of the wafer 1.

A cleaning vessel 108 is provided above the stage 102. A cleaningsolution 107 is charged into the cleaning vessel 103 for removing the Rufilm 23 deposited on the side surface and the back side of the wafer 1.The cleaning solution is applied to the upper surface (back side) of thewafer 1 through a nozzle 109, so that the back side and the side surfaceof the wafer 1, which is rotated while holding with the pins 103, arecleaned. When the rotation speed of the stage 102 is appropriatelycontrolled, the cleaning solution 107 can be spread toward the outeredge portion at the lower surface (device side) of the wafer 1.

Next, the composition of the cleaning solution 107 is illustrated.First, the etching rates of Ru with different types of cleaningsolutions used in a semiconductor production process are shown in FIG.15. A sample used was a 3 cm×4 cm square silicon chip on which a 100 nmthick Ru film has been deposited, and the thickness of the Ru filmetched per unit minute was measured. As shown in the figure, the etchingrate of Ru was 0.1 nm/minute or below for all the cleaning solutions. Itwill be noted that the rate of 0.1 nm/minute is a limit value of themeasurement of the device used. From the results, it will be seen thatthe known cleaning solutions used in the semi-conductor productionprocess do not enable Ru to be removed.

Then, the dissolving mechanism of Ru is described. In order to removethe Ru film 23, it is necessary to use chemicals capable of dissolvingRu. For the dissolution of Ru, it is also necessary to oxidize Ru. Theoxidation reaction of Ru proceeds according to the following formulas:

Ru+4H₂O→RuO₄+8H⁺+8e ⁻ (pH=0)

Ru+8OH⁻→RuO₄+4H₂O+8e ⁻ (pH=14)

The oxidation reduction potential (E) necessary for the reaction is at1.13 V for an acidic aqueous solution (pH=0) and at 0.30 V for analkaline aqueous solution (pH=14). Accordingly, for the oxidation of Ru,it is necessary to use an oxidizing agent whose oxidation reductionpotential is at a level of 1.13 V or over in an acidic aqueous solutionand is at 0.30 V or over in an alkaline aqueous solution.

FIG. 16 shows etching rates of Ru at predetermined concentrations ofdifferent types of oxidizing agents (except iodine) having oxidationreduction potentials larger than the above-mentioned values. It will benoted that the sample used and the measurement of the etching rate arethe same as in FIG. 15.

As shown, an oxidizing agent showing a great etching rate in an acidiccondition is only orthoperiodic acid (H₅IO₆). On the other hand,oxidizing agents having a great etching rate in an alkaline conditioninclude three compounds such as hypochlorous acid, metaperiodic acid andorthoperiodic acid. However, among the oxidizing agents showing a greatetching rate in an alkaline condition, hypochlorous acid andmetaperiodic acid are available in the form of a salt with an alkalimetal such as sodium (Na). Thus, these cannot be employed in thesemiconductor production process wherein contamination with an alkalimetal is not favored. Accordingly, the oxidizing agent, which can beused as the cleaning solution 107 for the Ru film among these oxidizingagents, is substantially orthoperiodic acid alone. The advantage of theoxidizing agent used in an acidic condition is that any salt with asolute is not formed, unlike an oxidizing agent used in an alkalinecondition.

FIG. 17 is a graph showing the relation between the concentration of anorthoperiodic acid aqueous solution (60° C.) and the etching rate(nm/minute) of Ru. As shown, it will be seen that when the concentrationof orthoperiodic acid in the aqueous solution is at about 10 wt % orover, the etching rate of Ru increases approximately in proportion tothe concentration of orthoperiodic acid. Accordingly, where anorthoperiodic acid aqueous solution is used as the cleaning solution 107of the Ru film 23, the concentration of orthoperiodic acid may be withina range of about 10 wt % to a saturation.

Further, we have found that when nitric acid is mixed with theorthoperiodic acid aqueous solution, the etching rate of Ru furtherincreases.

FIG. 18 is a graph showing the relation between the concentration ofnitric acid and the etching rate when Ru is etched by use of an aqueoussolution (temperature of 60° C.) obtained by adding nitric acid to anorthoperiodic acid aqueous solution having a concentration of 47 wt %(wherein a sample is the same as used in FIG. 15) As shown, when theconcentration of nitric acid is within a range of up to 2 mols/l, theetching rate increases substantially in proportion to the amount ofnitric acid.

FIGS. 19(a) to 19(d) are, respectively, tables showing the relationbetween the mixing ratio of nitric acid and the etching rate whenetching Ru with aqueous solutions (temperature of 60° C.) obtained byadding a nitric acid aqueous solution with a concentration of 69 wt % atratios of 0 (not added), 1, 2, 5 and 10 relative to 10 of orthoperiodicacid aqueous solutions having four concentrations (of 20 wt %, 30 wt %,40 wt % and 50 wt %) (the sample is the same as that used in FIG. 15).In all the cases, the addition of nitric acid results in a significantincrease in etching rate of Ru in comparison with the case usingorthoperiodic acid singly.

FIG. 20 is a graph showing the etching rate of Ru as a contour whereinthe concentrations of orthoperiodic acid and nitric acid in FIG. 19 arere-calculated as percent by weight. As shown, the aqueous solutionshaving a concentration of orthoperiodic acid of 20 wt % to 40 wt % and aconcentration of nitric acid of 20 wt % to 40 wt % exhibit a reducedvariation in the etching rate of Ru. Especially, it will be seen thatthe aqueous solutions having a concentration of orthoperiodic acid of 25wt % to 35 wt % and a concentration of nitric acid of 25 wt % to 35 wt%, indicated by broken lines in the figure, have a variation in theetching rate of Ru as small as about 10%.

From the above, where an aqueous solution containing orthoperiodic acidand nitric acid is used as the cleaning solution 107 of the Ru film 23,the concentrations of orthoperiodic acid and nitric acid are,respectively, within a range of 20 wt % to 40 wt %, preferably 25 wt %to 35 wt %, within which the variation in etching rate of Ru dependingon the variation in concentration of the cleaning solution 107 can besuppressed, thus enabling one to take a wide process margin. Moreparticularly, a mixed aqueous solution of orthoperiodic acid+nitric acidwithin the above-defined concentration ranges is used as a cleaningsolution suitable for the mass production process wherein a large numberof wafers are continuously processed.

The reason why mixing of nitric acid with an orthoperiodic acid aqueoussolution results in the increase of the etching rate of Ru is assumed asfollows. More particularly, orthoperiodic acid (H₅IO₆) is in anionization equilibrium in an aqueous solution as shown by the followingformulas.

H₅IO₆H₄IO₆ ⁻+H⁺

H₄IO₆ ⁻H₃IO₆ ²⁻+H⁺

H₃IO₆ ²⁻H₂IO₆ ³⁻+H⁺

H₄IO₆ ⁻IO₄ ⁻+H₂O

2H₃IO₆ ²⁻H₂IO₂O₁₀ ⁴⁻+2H₂O

Of these molecules and ionic species contained in the aqueous solution,one that has the capability of oxidizing Ru is only orthoperiodic acid(H₅IO₆) alone. When nitric acid is added to the orthoperiodic acidaqueous solution, the concentration of the proton (H⁺) derived fromnitric acid increases in the aqueous solution, so that the aboveequilibrium proceeds toward the left side. Eventually, the concentrationof orthoperiodic acid (H₅IO₆) capable of oxidizing Ru becomes high, fromwhich it is assumed that the etching rate of Ru increases.

Accordingly, the addition of an acid other than nitric acid and capableof permitting the equilibrium to proceed to the left side enables theetching rate of Ru to be increased. For instance, FIG. 21 shows thevariation in etching rate of Ru when different types of commerciallyavailable acids are, respectively, added to an orthoperiodic acidaqueous solution. As shown, the etching rate of Ru increases whenadding, aside from nitric acid, acetic acid.

Examples of the acid capable of increasing the etching rate of Ruincludes: carboxylic acids, typical of which are the above-indicatedacetic acid and HCOOH (formic acid);

hydrohalogenic acids such as HF (hydrofluoric acid), HBr (hydrobromicacid), HI (hydroiodic acid) and the like;

halogenated oxo acids such as HClO₃ (chloric acid), HClO₄ (perchloricacid), HBrO₃ (bromic acid), HBrO₄ (perbromic acid) and the like;

H₂S (hydrogen sulfide), hydrogen polysulfides such as H₂S₃, H₂S₄ and thelike, hydrides of elements of group 6 such as H₂Se (hydrogen selenide),H₂Te (hydrogen telluride) and the like;

oxo acids of sulfur such as H₂S₂O₃ (thiosulfuric acid), H₂S₂O₇(disulfuric acid), H₂SO₆ (polythionic acid), H₂SO₅ (peroxosulfuricacid), H₂S₂O₈ (peroxodisulfuric acid) and the like;

H₂SeO₄ (selenic acid), H₆TeO₆ (telluric acid) and the like;

polyphosphoric acids such as H₃PO₄ (orthophosphoric acid), H₄P₂O₇(pyrophosphoric acid), H₅P₃O₁₀ (triphosphoric acid), H₆P₄O₁₃(tetraphosphoric acid) and the like, and oxoacids of phosphorus, typicalof which is (HPO₃)_(n) (cyclo-phosphoric acid); and

H₃AsO₄ (arsenic acid), HN₃ (hydrogen azide), H₂CO₃ (carbonic acid),H₃BO₃ (boric acid) and the like.

Next, the cleaning method using the cleaning solution 107 made of anorthoperiodic acid aqueous solution or aqueous solutions mixed withdifferent types of acids indicated above is described with reference toFIGS. 12 to 14.

Initially, the wafer 1 deposited thereon with the Ru film 23 istransferred into the treating chamber of the cleaning device 100 whereinnitrogen gas is fed toward the upper surface of the stage 102 from thegas feed unit 105 thereby causing the wafer to be floated (FIG. 14).Next, the pins 103 are pressed against the side surfaces of the wafer 1to hold the wafer 1 horizontally (FIGS. 12, 13).

Subsequently, while rotating the stage 102, the cleaning solution 107 issupplied from the cleaning vessel 108 through a nozzle 109 toward theupper surface (back side) of the wafer 1, thereby cleaning the back sideand the side surface of the wafer 1. If necessary, the outer edgeportion at the lower surface (device side) of the wafer 1 is alsocleaned. The cleaning solution 107 used may be a mixed aqueous solutionmade, for example, of orthoperiodic acid (concentration of 30 wt %) andnitric acid (concentration of 30 wt %), both heated to 60° C.

During the course of the cleaning, the pins 103 in contact with thewafer 1 are each rotated within a horizontal plane. In this way, thewafer 1 is rotated by the frictional force with the pins 103, so thatthe side portions in contact with the pins 103 are changed to clean theentire side surfaces of the wafer 1. It will be noted that the cleaningdevice used herein is described in detail in our Japanese PatentApplication No. Hei 11-117690.

The cleaning of the back side and the side surface of the wafer 1 usingthe cleaning solution 107 of this embodiment may be carried out by useof a device other than the above-stated cleaning device 100, e.g. theknown Bernoulli chuck-type pin etching device. Prior to the cleaning ofthis embodiment, the back side of the wafer 1 may be subjected to brushcleaning.

The etching rate of the Ru film 23 with the above-mentioned mixedaqueous solution of orthoperiodic acid+nitric acid (60° C.) was found tobe 2.244×10⁻³ g/minute on the weight basis. In contrast, the etchingrate of Ru with a solution (100° C.) of 33% HIO₃:20% ICI=1:1 in the caseof the afore-referenced Japanese Laid-open Patent Application No. Hei7-157832 was at 1.567×10⁻⁶ g/minute, or the etching rate of Ru with asolution (70° C.) of 37% HI+0.01 mol/liter of 12 in the case of theafore-referenced Japanese Laid-open Patent Application No. Hei 7-224333was at 0.9625×10⁻⁶ g/minute, thus both being very small. Quantitativelyit may be said that Ru is not substantially dissolved. Moreparticularly, according to the method of the invention, Ru can bedissolved at an etching rate as high as not less than 1000 times that ofthese prior art techniques. In addition, the method of the invention isadvantageous in that Ru can be dissolved at a temperature lower than insolutions of the prior art techniques.

Next, the method of forming a lower electrode using the Ru film 23 as anelectrode material is described. First, the wafer 1, obtained aftercompletion of the cleaning treatment, is transferred to an inspectiondevice for common use shown in FIG. 10, in which the degree ofcontamination at the back side and the side surface is checked.Thereafter, the wafer 1 is annealed (thermally treated) in an atmosphereof nitrogen at about 700° C. by use of a common use annealing (thermaltreating) device, thereby causing the stress of the Ru film 23 to bereleased.

Thereafter, the wafer 1 is transferred to a CVD device (not shown), anda silicon oxide film 24 is deposited on the Ru film 23 as shown in FIG.22. For the dry etching of the Ru film 23, an oxygen-based gas is used,so that an oxidation-resistant material, such as the silicon oxide film24, is used as an etching mask.

Next, the wafer 1 is subjected to a lithographic step using the commonuse devices shown in FIG. 10. More particularly, as shown in FIG. 23,the silicon oxide film 24 is dry etched through the mask of aphotoresist film 24 deposited on the silicon oxide film 24, therebyforming a hard mask for dry etching the Ru film 23.

The photoresist film 25 is removed by ashing, after which, as shown inFIG. 24, the Ru film 23 is dry etched through the mask of the siliconoxide film 24 to form a lower electrode 23A of an information storagecapacitor element. For the etching of the Ru film 23, a mixed gas, forexample, of oxygen gas and chlorine gas is used. The etching system usedincludes an inductively coupled plasma etching system, an ECR (electroncyclotron resonance) plasma etching system, an ICP (inductively coupledplasma) etching system, a magnetron RIE (reactive ion etching) plasmaetching system, a helicon plasma etching system or the like. The Ru film23 is etched by use of the lower TiN film 19 as an etching stopper whilemonitoring light with a wavelength of 406 nm, which is, for example, anemission peak of Ti.

In order to remove the etching residue of the Ru film 23, the wafer 1 iscleaned by use of the cleaning device shown in FIGS. 12 to 14. To thisend, such a mixed aqueous solution of orthoperiodic acid+nitric acid asset out before is used as a cleaning solution, thereby permitting the Ruresidue to be satisfactorily removed from the side surface and back sideof the wafer 1.

As shown in FIG. 25, the TiN film 19 is dry etched through the mask ofthe silicon oxide film 24. For the etching of the TiN film 19, a mixedgas, for example, of boron trichloride (BCl₃) and chlorine is used. Theetching system is, for example, an ECR plasma etching system.

Next, after removal of the silicon oxide film 24 by dry etching, a BSTfilm 26 serving as a capacitance insulating film is deposited on thelower electrode 23A by a CVD method. Subsequently, the wafer 1 iscleaned by means of the cleaning device shown in FIGS. 12 to 14 toremove the BST film 26 deposited on the side surface and back side ofthe wafer 1. For this purpose, the cleaning liquid used is, for example,hdyrofluoric acid.

As a material for the capacitance insulating film, there may be used,aside from the BST used as the film 26, high dielectric materials suchas Ta₂O₅ (tantalum oxide), and ferrodielectric materials having aperovskite crystal structure such as PZT, PLT, PLZT, SBT, PbTiO₃,SrTiO₃, BaTiO₃ and the like. In this case, the wafer 1 is cleaned by useof the cleaning device shown in FIGS. 12 to 14, an unnecessaryhigh/ferro-dielectric film deposited on the side surface and back sideof the wafer can be removed. For a cleaning solution of these materials,there is used, for example, hydrofluoric acid of a high concentration.

For removing crystal defects of the BST film 26, the wafer is annealed(thermally treated) in an atmosphere of oxygen at about 700° C. Wherethe high dielectric material such as Ta₂O₅, or a ferrodielectricmaterial having a perovskite crystal structure such as PZL, PLT, PLZT,SBT, PbTiO₃, SrTiO₃ or BaTiO₃ is used, the wafer 1 is annealed(thermally treated) in an atmosphere of oxygen in order to removecrystal defects.

As shown in FIG. 27, an Ru film 27 used as an upper electrode materialis deposited on the BST film 26 by a CVD method. In this case, after theformation of the Ru film 27, the wafer 1 is cleaned by use of thecleaning device shown in FIGS. 12 to 14. When a mixed aqueous solutionof orthoperiodic acid and nitric acid is used as a cleaning solution,the Ru film 27 deposited on the side surface and back side of the wafer1 can be removed satisfactorily.

In this way, there is completed information storage capacitor element Cwhich is constituted of the lower electrode 23A made of the Ru film 23,the capacitance insulating film made of the BST film 26, and the upperelectrode made of the Ru film 27. According to the steps describedhereinabove, the memory cells of DRAM, which are constituted of MISFETsfor memory cell and information storage capacitor elements C connectedin series therewith are completed.

Thereafter, as shown in FIG. 28, a silicon oxide film 28, a siliconnitride film 29 and a silicon oxide film 30 are successively depositedover the information storage capacitor element C by a CVD method. Awiring groove 31 is formed in the silicon oxide 30 by dry etchingwherein the silicon nitride film 29 is used as an etching stopper,followed by formation of a buried Cu wiring 33 inside the wiring groove31 via a barrier metal film 32.

For the formation of the buried Cu wiring 33, the barrier metal 32 made,for example of a TiN film, a TaN film or the like is deposited insidethe wiring groove 31 and on the silicon oxide film 30 by a sputteringmethod (or a CVD method), followed by further deposition of a Cu film(33) on the barrier metal film 32 by a sputtering method.

In order to remove the Cu film deposited on the side surface and backside of the wafer 1, the wafer 1 is cleaned by use of the cleaningdevice shown in FIGS. 12 to 14. For the cleaning solution, there isused, for example, nitric acid or concentrated sulfuric acid. Thiscleaning enables one to prevent the wafers 1 in the lower layers steps(including the initial element formation step and wiring step prior tothe formation of the gate insulating film) from contamination with Cu.

Next, the Cu film (33) is annealed (thermally treated) so that the Cufilm (33) is satisfactorily buried inside the wiring groove 31, followedby formation of a buried Cu wiring 33 according to a so-called Damascenemethod wherein an unnecessary Cu film (33) outside the wiring groove 31is removed by a chemical mechanical polishing method. It will be notedthat the method of forming the buried Cu film 33 is described in detailin Japanese Patent Application No. Hei 11-117690 (Tanabe).

The invention of the present inventors has been particularly describedbased on the embodiments thereof, which should not be construed aslimiting the invention and may be modified or altered in various wayswithout departing from the spirit of the invention.

For instance, in the above embodiments, the use of an aqueous solutionas the cleaning solution, which makes use, as a solvent, of water havingno problem on the reaction with a solute and the contamination of awafer, has been described. The invention is not limited to such use, andfor instance, an organic solvent or an inorganic solvent other thanwater may be used.

In the embodiments, the case where Ru is used as electrodes of acapacitor has been set out. The wafer cleaning method of the inventionmay be applied to the case where the capacitor electrodes areconstituted of platinum group metals other than Ru, e.g. Pt (platinum),Ir (iridium), Rh (rhodium), Pd (palladium), Os (osmium) and the like.For a cleaning solution for the electrode made of Ir, orthoperiodic acidor the like may be used. For a cleaning solution of Pt, aqua regia isused, and the a cleaning solution of Pd, aqua regia or concentrationnitric acid is used.

The invention is applicable not only to DRAM using a transitionmetal-containing film as a capacitor material, but also CMIS integratedcircuits wherein a gate insulating film of MISFET is constituted, forexample, of a high dielectric material such as Ta₂O₅ (tantalum oxide).

The effects obtained by typical embodiments disclosed in the inventionare briefly described below.

According to the invention, in the semiconductor mass production processwherein a lithographic device, inspection devices, an annealing deviceand the like are commonly used in an initial element formation step, awiring step and a transition metal-containing film processing step priorto the formation of a gate insulating film, the contamination of wafers,subjected to the initial element formation step and the wiring step byuse of the above devices, with a transition metal can be reliablyprevented.

EXAMPLE 2

The summary of another example of the invention can be itemized in thefollowing way.

1. A method of treating a solid surface wherein a treating solutioncontaining an oxidizing agent is fed to the solid surface to subject thesolid surface to etching treatment, characterized in that the oxidizingagent is able to yield an oxygen atom to the solid surface and has anoxidation reduction potential higher than that of the solid.

2. A method of treating a solid surface as recited in 1 above,characterized in that the treating solution comprises at least one of ahypochlorite ion, a chlorite ion, a chlorate ion, a perchlorate ion, ahypobromite ion, a bromite ion, a bromate ion, a perbromate ion, ahypoiodite ion, an iodite ion, an iodate ion, a periodate ion, apermanganate ion, a chromate ion, a dichromate ion, a nitrate ion and anitrite ion, and the treating solution is fed to the solid surface.

3. A method of treating a solid surface as recited in 1 above,characterized in that the solid contains, at least, ruthenium or osmium.

4. A treating solution of the type which is fed to a solid surface foretching the surface, characterized in that the solution contains anoxidizing agent for yielding an oxygen atom, at least, to the solidsurface, and the oxidizing agent has an oxidation reduction potentialhigher than that of the solid.

5. A treating solution as recited in 4 above, characterized in that thetreating solution comprises at least one of a hypochlorite ion, achlorite ion, a chlorate ion, a perchlorate ion, a hypobromite ion, abromite ion, a bromate ion, a perbromate ion, a hypoiodite ion, aniodite ion, an iodate ion, a periodate ion, a permanganate ion, achromate ion, a dichromate ion, a nitrate ion and a nitrite ion.

The invention relates to a treating solution and method of a solidsurface in an electronic device production process, and moreparticularly, to a treating solution and method suitable for theproduction of a semiconductor device, a heating resistor and the like.

In general, the process of dissolving a solid, such as a metal, in atreating solution by chemical reaction between the solid and thetreating solution in an electronic device production process has beenwidely applied to an etching method, which is one of solid processingmethods, a cleaning method of removing a specific foreign matter from asolid surface, and the like. The treating solution is a fluid or astationary body containing at least a liquid, and may be made of aliquid phase alone, a combination of a liquid phase and a gas phase, anda combination of a liquid phase and a solid phase. Moreover, the liquidphase in the treating solution may be constituted of two or more liquidphases without limitation.

However, for carrying out a reaction such as of etching or dissolutionof the solid, an oxidizing agent is essentially required. For instance,where copper is etched, there is used, as an oxidizing agent, apotassium hexacyanoferrate (III) aqueous solution, a sodium acidicperoxodisulfate aqueous solution or the like. The metal such as copper,chromium or the like is oxidized by means of these oxidizing agents andis dissolved in the solution by bonding to an appropriate ligand. Thisligand may be the molecules of a solvent, e.g. the molecules of water,to which ammonia or a cyanide may be added, if necessary.

On the other hand, in the production step of an electronic device suchas a silicon semiconductor, it is usual to mainly use hydrogen peroxideas an oxidizing agent. The reason for this is that where an oxidizingagent containing a metal element such as a hexacyanoferrate (III) ion isused, there is the apprehension that the semiconductor device may benewly contaminated with the metal element contained in the oxidizingagent, and thus, the use of a metal element-free oxidizing agent isessential and a technique of rendering hydrogen peroxide highly pure hasbeen established, hydrogen peroxide can be readily utilizedindustrially.

For one instance, a metal such as cobalt, titanium or the like, which isused in the formation step of a source electrode and a drain electrodeon an electric field effect transistor, is dissolved in an aqueoussolution made of hdyrochloric acid and hydrogen peroxide, or an aqueoussolution made of ammonia and hydrogen peroxide. For the removal of ametal element from the surface of a semiconductive wafer, there is wellused an aqueous solution containing hydrochloric acid and hydrogenperoxide, an aqueous solution containing sulfuric acid and hydrogenperoxide, or an aqueous solution containing hydrofluoric acid andhydrogen peroxide.

The conditions which an oxidizing agent should satisfy include anoxidation reduction potential of an oxidizing agent used higher thanthat of a solid to be processed. More particularly, with the etching ofcopper in prior art example, for instance, as set out in The Handbook ofChemistry, Revised Edition 4, Fundamentals II (hereinafter referred toas literature 1), the oxidation reduction potential of Cu²⁺/Cu is at0.340 V (based on the standard hydrogen electrode: the potential ishereinafter referred to as that based on the standard hydrogenelectrode). The oxidation of copper is promoted by means of thehexacyanoferrate (III) ion (oxidation reduction potential: 0.361 V) orperoxodisulfate ion (oxidation reduction potential: 1.96 V), but theoxidation reaction of oxygen does not take place by means of ahexacyanochromate (III) ion (oxidation reduction potential: −1.14 V).

Accordingly, the above electrochemical reaction has to be taken intoaccount with respect to the etching treatment of a metal, which isemployed in recent advancement, such as of a high degree of integration,a high speed and the like, of semiconductor devices, e.g. a noble metalsuch as ruthenium.

However, hydrogen peroxide, which has been hitherto, ordinarily employedin the art, cannot be used for dissolution of a noble metal such asruthenium or the like. More particularly, in spite of the fact thathydrogen peroxide has an oxidation reduction potential (oxidationreduction potential of H₂O₂/H₂O of 1.763 V at pH=0, from literature 1)higher than the oxidation reduction potential of ruthenium, asatisfactory etching rate of ruthenium with a treating solution usinghydrogen peroxide cannot be obtained.

Moreover, when using a chemical solution containing a peroxodisulfate ornitric acid, which has been conventionally used for etching or copper oriron, it has been difficult to obtain a satisfactory etching rate for anoble metal such as ruthenium or the like.

In view of the above-stated circumstances in the art, there has beenwidely demanded a development of a treating solution, which has anadequate etching rate against the noble metal, in the production processof semiconductor devices. If this can be realized, semiconductor devicesexhibiting an excellent performance are obtainable, thus contributinggreatly to the development in the industrial field such as ofcommunication, information, picture display and the like.

For instance, it is known that ruthenium, which is one of platinumgroup, noble metal elements, is very unlikely to undergo oxidation, sothat it is necessary to use an oxidizing agent having an intenseoxidizing force, or a high oxidation reduction potential for itsoxidation treatment.

When taking the etching of ruthenium into account, it is necessary toconvert ruthenium into ruthenium tetraoxide (RuO₄) wherein ruthenium isbonded to four oxygen atoms, thereby ensuring the dissolution thereof.

The standard electrode potential of ruthenium and ruthenium tetraoxideis at 1.13 V at pH 0 (M. Pourbaix: “Atlas of Electrochemica Equilibirain Aqueous Solutions”, 1st English Edition, Chapter IV, Pargamon, Oxford(1996), hereinafter referred to as literature 2). The potential at whichruthenium tetraoxide is electrochemically formed from ruthenium furtherincreases, including an overpotential, and is reported to be at 1.4 to1.47 V (literature 2) Accordingly, an oxidizing agent used to etchruthenium, for example, at pH=0 should have an oxidation reductionpotential of, at least, 1.13 V, preferably 1.4 V or over.

For the dissolution by oxidation of ruthenium, the bonding to oxygen isessential as will be seen from the reaction formula of the product.Accordingly, mention may be made, as a candidate for a source ofsupplying an oxygen atom, of an oxidizing agent or water. In thisconnection, the activity of water is kept substantially constant in anaqueous solution, so that it is effective for efficient oxidationdissolution of ruthenium to use an oxidizing agent which is able topositively release an oxygen atom.

In other words, it is necessary that an oxidizing agent used to form acompound bonded with oxygen and efficiently dissolve such a compound aswith the case of a noble metal such as ruthenium have an oxidationreduction potential higher than the oxidation reduction potential of thedissolution reaction of a metal to be dissolved out and that theoxidizing agent be able to release an oxygen atom in the course of thereaction.

It will be noted that the oxidizing agent capable of releasing an oxygenatom in the course of the oxidation reaction means one which isdescribed below: the oxidizing agent is such an agent that when an atomwhose oxidation number is reduced during the reaction is calledoxidation center atom among the atoms constituting an oxidizing agent,one or plural oxygen atoms bonded to the oxidation center atom cut offbonding with the oxidation center atom and freshly join to an atom to beoxidized.

Next, the mechanism of efficiently dissolving ruthenium by oxidationwith an oxidizing agent capable of releasing an oxygen atom is nowdescribed.

A number of reports have been provided with respect to the oxidationreaction of a ruthenium ion, not a ruthenium metal, and for example, anitrosylruthhenium ion ([Ru¹¹(NO)]₃ ⁺) is oxidized into rutheniumtetraoxide by means of nitric acid or a cerium (IV) ion.

However, according to our study, ruthenium metal is not oxidized anddissolved with nitric acid or a cesium (IV) ion. The reason whyruthenium metal is not oxidized and dissolved by means of nitric acid isthat nitric acid does not have an oxidation reduction potential (astandard electrode potential of HNO₃/NO₂ ⁻ is at 0.835 V: literature 1)necessary for the oxidation of the ruthenium metal.

The reason that ruthenium is not oxidized and dissolved by means of thecerium (IV) ion is that as shown in the following formula (1), anyoxygen atom is not released i-n the course of the reaction

Ce₄ ⁺ +e ⁻→Ce₃ ⁺  (1)

From the above, it will be seen that whether or not an oxidizing agentis able to release an oxygen atom does not take great part in a furtheroxidation process of a ruthenium ion having a positive oxidation number,but the release of an oxygen atom from an oxidizing agent is essentialfor the process of oxidizing and dissolving a ruthenium metal having anoxidation number of 0.

The metal to be dissolved is not limited to ruthenium, and the above maybe applied to other noble metal such as, for example, osmium. Theoxidizing agent suited for the dissolution of these noble metalscontains an oxygen atom-donating oxidizing agent. Such an oxidizingagent may be ones which contain any one of a hypochlorite ion, achlorite ion, a chlorate ion, a perchlorate ion, a hypobromite ion, abromite ion, a bromate ion, a perbromate ion, a hypoiodite ion, aniodite ion, an iodate ion, a periodate ion, a permanganate ion, achromate ion, a dichromate ion, a nitrate ion and a nitrite ion.

Other examples of the invention are described in detail.

A ruthenium metal as a typical example of a noble metal was used, andthe etching effect of oxidizing agents containing different types ofions was determined, with the results shown in Table 1.

Etching was performed according to a well-known procedure. Moreparticularly, a ruthenium thin film (with a film thickness of 200 nm)was formed on a silicon wafer (20×40 mm) according to an ordinarysputtering method. A photoresist film was applied onto part of theruthenium thin film and baked by a well known method, followed byimmersion of the wafer in a solution containing an oxidizing agent atroom temperature for 10 to 30 minutes. Thereafter, the wafer was wellwashed with water and the photoresist film was removed by a well-knownmethod, followed by measuring an etching step formed on the surface ofthe ruthenium thin film by means of an ordinarily employed contactfinger-type step meter The measurement of a film thickness may not belimited to the above method, but a method using, for example, afluorescent X-ray may be used without limitation.

TABLE 1 Oxidation reduction potential of oxidizing agents anddissolution rate of ruthenium Oxidation reduction Dissolution ratepotential (V) (nm/min) Peroxodisulate ion 1.96 <0.1 Hydrogen peroxide1.76 <0.1 Hypochlorite ion 1.72 82.4 Cesium (IV) ion 1.61 <0.1 Periodateion 1.60 13.7 Borate ion 1.52 5.5 Nitric acid 0.84 <0.1 Iodine 0.54 <0.1

As will be apparent from these results, little dissolution of rutheniummetal was recognized when using oxidizing agents containing hydrogenperoxide, cerium (IV) ion, nitric acid and iodine, and a remarkabledegree of etching of ruthenium was recognized when using thehypochlorite, bromate and periodate

These oxidizing agents can release an oxygen atom in the followingreactions.

ClO⁻→Cl⁻+(O)  (2)

BrO₃ ⁻→Br⁻+3(O)  (3)

IO₄ ⁻→IO₃ ⁻+(O)  (4)

H₄IO₆ ⁻→IO₃ ⁻+2H₂O+(O)  (5)

On the other hand, there are some oxidizing agents having an oxidationreduction potential enough to oxidize the ruthenium metal, with whichetching of the ruthenium metal was scarcely recognized. For instance, aperoxodisulfate or iodine does not release any oxygen atom as will beseen in the following reaction formulas.

S₂O₈ ²⁻+2e ⁻→2SO₄ ²⁻  (6)

I₂+2e ⁻→2I⁻  (7)

Accordingly, since the oxygen atom to be bonded to ruthenium is notsupplied from the oxidizing agent, the etching of ruthenium metal doesnot proceed, or it can be said that the etching is so slow as not to beconfirmed by an ordinary method.

The difference in behavior between the oxidizing agent capable ofreleasing an oxygen atom and the oxidizing agent incapable of releasingan oxygen atom as illustrated above is schematically shown in FIG. 29.

As for hydrogen peroxide, there are two reactions including a reactionwherein an oxygen atom is released (formula 8) and a reaction wherein anoxygen atom is not released but the peroxide is decomposed into twoOH⁻ions (formula 9).

H₂O₂+2e ⁻→2OH⁻  (8)

I₂+2e ⁻→2OH⁻  (9)

However, as will be apparent from the results of Table 1, the etching ofruthenium metal is not recognized, so that it is considered that with atreating solution made of hydrogen peroxide, the reaction (9) proceeds.As stated above, although the oxidation reduction potential of hydrogenperoxide is larger than that of ruthenium metal, any oxygen atom is notreleased in the reaction, thus disenabling the etching to proceed.

In FIG. 29, (a) shows the case where an oxidizing agent incapable ofreleasing oxygen atom 101, i.e. iodine, is used. Iodine atom 102 isconverted to two iodide ions through the reaction, and any oxygen atom101 is not released.

As a consequence, ruthenium metal does not receive any oxygen atom 101and cannot be converted to ruthenium tetraoxide (RuO₄) 111 and is notdissolved. On the other hand, FIG. 29(b) shows the case where there isused metaperiodate ion 113 serving as an oxidizing agent capable ofreleasing the oxygen atom 101. Metaperiodate has four oxygen atoms inone ion and releases one atom in the course of the reaction, resultingin iodate ion 112 having three oxygen atoms. Ruthenium receives theoxygen atom 101 released during the reaction, and converts to rutheniumtetraoxide 111 and is thus dissolved.

As stated above, where a noble metal such as ruthenium metal isdissolved for etching, a treating solution therefor should contain, atleast, hypochloric acid, bromic acid or periodic acid, by which thetreatment can be carried out within a range of practical time.

It is to be noted that the treating solution should not be construed aslimiting to those solutions containing hypochloric acid, bromic acid orperiodic acid, but any solutions containing an oxidizing agent capableof releasing an oxygen atom, or an oxygen atom-donating oxidizing agent,ensures a similar treating effect, like this example.

EXAMPLE 3

The processing example of an electronic device is illustrated as Example3 with reference to FIG. 30.

FIG. 30 is a flow chart wherein a recess 2 and a protrusion 3 are formedon a substrate 1 according to a well-known processing method, e.g. a wetetching method, a dry etching method or a mechanical polishing method,on which a ruthenium thin film 11 is formed, for example, by awell-known sputtering method.

Next, a colloidal silica solution is applied thereon in an appropriateamount and dried to cover the recess 2 alone with the colloidal silica12. Thereafter, the substrate 1 is immersed in a 10% potassiumhypochlorite aqueous solution to remove the ruthenium thin film from theprotrusion 3, thereby forming a cup-shaped ruthenium film pattern on theside and bottom surfaces of the recess 2.

Thus, in the production process of an electronic device wherein theruthenium thin film is formed only inside the groove provided in thesubstrate through etching of the ruthenium thin film, when a solutioncontaining an oxygen atom-donating oxidizing agent, e.g. a solutioncontaining a hypochlorous acid, is used, the etching treatment can becarried out within a range of a practical time, thus enabling one tomake an electronic device.

It will be noted that the treating solution is not limited to a solutioncontaining a hypochlorous acid, and a similar treating effect can beobtained as in this example when using a solution which contains anoxygen atom-donating oxidizing agent such as bromic acid or periodicacid.

EXAMPLE 4

Examples 4 is described with reference of FIG. 31 Where the rutheniumfilm 11 is formed on the substrate 1 set out in Example 1, there are amultitude of ruthenium fine particles 51 in a film formation chamber ofthe device. Accordingly, the substrate 1, on which the ruthenium thinfilm 11 has been formed on one surface thereof, is deposited on theother surface with a multitude of ruthenium fine particles.

For one instance, when the concentration of ruthenium, which is presentin a surface (a back surface) opposite to the surface of the substrate 1on which the ruthenium thin film 11 has been formed, was measured by awell-known total reflection fluorescent X-ray analysis, with the resultthat the number of the fine particles was found to be at 2×10¹⁸atoms/m². A 50% orthoperiodic acid aqueous solution was supplied only tothe back surface of the substrate 1, followed by washing for 2 minutes.As a result, the concentration was reduced to 2×10¹⁵ atoms/m².

In this way, not only the etching of a noble metal thin film, but alsothe removal of noble metal fine particles deposited on a substrate canbe effectively carried out by supplying a solution containing an oxygenatom-donating oxidizing agent to the substrate surface deposited withthe fine particles to be removed.

EXAMPLE 5

A fifth example is described.

In this example, a noble metal to be treated is osmium, and the osmiummetal is converted to osmium tetraoxide (OsO₄) through the reactionsimilar to the case of ruthenium metal and is thus dissolved.

For one instance, a substrate whose surface is contaminated with thefine particles of an osmium metal was cleaned in a manner set out inExample 3. As a result, the concentration of the osmium fine particlesexisting in the substrate prior to the cleaning was found to be at5×10¹⁸ atoms/m². When the substrate was cleaned by use of an about 1mol/l potassium permanganate aqueous solution adjusted to pH=1 for about5 minutes, the concentration of the fine particles was reduced to 5×10¹⁵atoms/m².

Using a treating fluid of the invention, the etching and dissolution ofa metal solid, which have been hitherto difficult, become possiblewithin a range of a practical time.

What is claimed is:
 1. A fabrication method of a semiconductorintegrated circuit device comprising the steps of: (a) forming aninsulating film over a device surface of a wafer; (b) forming a wiringgroove in the insulating film by first lithographic treatment; (c)depositing a copper film over the insulating film and in the wiringgroove in the insulating film over the device surface; (d) after step(c), cleaning an outer edge portion of the device surface and an entirearea of a back surface of the wafer with cleaning liquid, which candissolve copper, without applying the cleaning liquid to a centralregion of the device surface; (e) removing the deposited copper filmoutside the wiring groove by chemical mechanical polishing; (f) aftersteps (d) and (e), subjecting the wafer to a second lithographictreatment without subjecting the wafer to any lithographic treatmentbetween steps (b) and (f).
 2. A fabrication method of a semiconductorintegrated circuit device as defined in claim 1, wherein step (d) isperformed before step (e).
 3. A fabrication method of a semiconductorintegrated circuit device as defined in claim 1, wherein the cleaningliquid is nitric acid or sulfuric acid.